Bifurcated catheter assembly

ABSTRACT

A bifurcated catheter assembly is provided for treating bifurcated vessels. The bifurcated catheter assembly comprises an elongate main catheter shaft having a stiffer proximal portion, a more flexible distal portion, and a pair of branch catheters attached to the distal portion. An expandable member is located on each of the branch catheters. The balloons are held together to provide a low profile as the device is advanced over the tracking guide wire. Upon reaching the bifurcated vessel, the balloons separated and are advanced over separate guide wires into separate branches of the bifurcated vessel. The bifurcated catheter assembly can be used to dilate a stenoses or deliver and implant a Y-shaped stent in the bifurcation.

This application is a continuation of U.S. Ser. No. 09/542,371, filedApr. 4, 2000, now U.S. Pat. No. 6,210,380, which is a continuation ofU.S. Ser. No. 09/138,844, filed Aug. 24, 1998, now U.S. Pat. No.6,117,117.

BACKGROUND OF THE INVENTION

The present invention relates in general to balloon catheters employedin the treatment of vascular diseases. More particularly, the presentinvention relates to a bifurcated catheter assembly which has twodilation balloons in parallel at the distal end of a single cathetershaft. The bifurcated catheter assembly provides an improved means fortreating arterial bifurcations.

In a medical procedure known as percutaneous transluminal coronaryangioplasty (PTCA), a balloon catheter is used to treat a coronaryartery (or other vessel) which has become narrowed or restricted due tothe accumulation of plaque along the artery wall. In the PTCA procedure,a balloon catheter is inserted percutaneously and is advanced throughthe lumen of the coronary artery to the site of a stenosis. The balloonis then inflated to press the plaque against the artery wall therebydilating the lumen of the artery and establishing adequate blood flow.

After the PTCA procedure has been performed, a stent (which is wellknown in the art) may be deployed in the treated area to preventrestenosis and maintain a clear pathway for the flow of blood. A ballooncatheter with an expandable stent mounted over the balloon is advancedthrough the lumen until the stent is in the desired location. Theballoon is then temporarily inflated thereby expanding and implantingthe stent in the vessel. The balloon is then deflated and the ballooncatheter assembly is removed from the lumen, leaving the implanted stentin the vessel to support the vessel wall and prevent development ofrestenosis.

Although most diseased arteries can be successfully treated in thismanner using conventional balloon catheters and stents, arteries whichare diseased at a bifurcation are difficult to treat with the devicescurrently available. For example, when a conventional balloon catheteris used to treat one of the vessel passages at a bifurcation duringPTCA, the pressure from the expansion of the balloon in the treatedpassage can restrict the flow of blood to the untreated passage bypushing the carina over the ostium of the untreated vessel. In addition,the pressure of the balloon in the treated passage may shift the plaquefrom the treated passage to the untreated passage. If sufficient plaqueis shifted to the untreated passage, the ostium of the untreated passagecan becomes so occluded that it becomes difficult or impossible toinsert a guide wire and catheter to perform a PTCA in the untreatedvessel.

Deploying a stent at a bifurcation is also very challenging because thestent must overlay the entire diseased area of the bifurcation, yet notitself compromise blood flow. Conventional stents are designed to repairareas of blood vessels that are removed from bifurcations and, since aconventional stent generally terminates at right angles to itslongitudinal axis, the use of conventional stents in the region of avessel bifurcation may result in blocking blood flow of a side branch(commonly referred to as “jailing” the side branch) or fail to repairthe bifurcation to the fullest extent necessary. To be effective, thestent must overlay the entire circumference of the ostium to a diseasedportion and extend to a point within and beyond the diseased portion.Where the stent does not overlay the entire circumference of the ostiumto the diseased portion, the stent fails to completely repair thebifurcated vessel.

To overcome the problems and limitations associated with the use ofconventional stents, a Y-shaped stent has been proposed for thetreatment of bifurcations. Such a stent has the advantage of completelyrepairing the vessel at the bifurcation without obstructing blood flowin other portions of the bifurcation. In addition, such a stent allowsaccess to all portions of the bifurcated vessel should furtherinterventional treatment be necessary. In a situation involving diseasein the origin of an angulated aorta-ostial vessel, such a stent wouldhave the advantage of completely repairing the vessel origin withoutprotruding into the aorta or complicating repeat access. The proposedY-shaped stent provides an improved device for repairing bifurcations,however, the delivery and deployment of such a stent cannot be easilyaccomplished with a conventional balloon catheter.

Because a conventional balloon catheter is not adequate for treating anarterial bifurcation, many physicians currently employ a “kissingballoons” technique in which two separate balloon catheters are insertedinto a guide catheter and each balloon tracks over a separate guidewire. The guide catheter is advanced to a point proximal of thebifurcation site and two guide wires are then advanced from the distalend of the guide catheter into separate vessel passages. The two ballooncatheters then track the guide wires into the respective passages. Theballoons are simultaneously inflated using either separate inflationmedia or from a single source using a manifold which divides the flow.The two catheters are used together for PTCA or stenting so that bothvessel passages at a bifurcation site can be treated simultaneously.

Although generally effective, the use of two single balloon catheters totreat arterial bifurcations has significant drawbacks. For example, thepresence of two similar catheters exiting the proximal end of the guidecatheter makes it difficult for a physician to manage both deviceswithout becoming confused as to which catheter controls which balloon.Furthermore, the presence of two balloon catheters within one guidecatheter creates a large device profile thereby limiting the amount ofradiopaque dye which can be injected into the vessel to allow thephysician to view the bifurcation.

Efforts have been made to develop a balloon catheter which is designedspecifically for the treatment of arterial bifurcations. Such effortshave led to the proposal of a Y-shaped balloon disposed at the distalend of a catheter which is inflated in a bifurcation to treat bothpassages simultaneously. Although a Y-shaped balloon would provide animprovement over the use of two separate balloon catheters, the proposeddevice may not be practical due to challenges of manufacturing aY-shaped balloon, attaching it to a catheter shaft, and properlypositioning it at a bifurcated blood vessel. A device of this type isdescribed in the international patent application WO 97/16217 dated Oct.30, 1995 and entitled Angioplasty Device for Arterial Bifurcation.

Thus, there exists a need for an improved balloon catheter which can beused to effectively treat arterial bifurcations both for PTCA and stentdelivery and deployment. It is also desirable that such a ballooncatheter be easy to use, inexpensive to manufacture, and constructedfrom materials which are common in the industry today. The presentinvention addresses this need.

SUMMARY OF THE INVENTION

The present invention provides a bifurcated catheter assembly which canbe used to simultaneously dilate stenoses in both the main and the sidebranch vessels of a bifurcation and also provides a means to quickly andeasily deliver and deploy a Y-shaped stent. The invention comprises asingle catheter shaft having two individual parallel balloons at thedistal end. The parallel balloons track separate guide wires intoseparate blood vessel passages at a bifurcation and are inflatedsimultaneously by inflation media from a common source. The presentinvention is designed primarily for use in coronary arteries, however,it may also be used to treat other vessels such as the renals, abdominalaorta, femoral, and carotid arteries.

The bifurcated catheter assembly of the present invention includes amain catheter body with three lumens in its distal portion. The firstlumen is an inflation lumen for pressurized inflation media which isused to inflate and deflate the balloons. The second lumen is a guidewire lumen which contains the tracking guide wire and the third lumen isalso a guide wire lumen which contains an integrated guide wire.

Two parallel catheter branches are connected to the distal end of themain catheter body. Each of the parallel catheter branches has twolumens. One lumen is an inflation lumen which communicates with theinflation lumen in the main catheter body and the other lumen is a guidewire lumen in communication with one of the guide wire lumens in themain catheter body. An expandable member such as a balloon is located onthe periphery of each catheter branch which is in communication with theinflation lumen in each catheter branch. An inflation notch on the sideof each catheter branch allows pressurized inflation media to enter andexit the balloons. The guide wire lumen in each catheter branch extendsall the way to the distal end allowing the guide wires to exit distallyfrom the respective branches.

The tracking guide wire is advanced through the main vessel and theintegrated guide wire is advanced through the ostium and into the sidebranch vessel at the bifurcation. With one guide wire advanced into eachpassage of the bifurcation, the bifurcated catheter assembly is advancedso that the first balloon tracks the tracking guide wire into the mainvessel passage and the second balloon tracks the integrated guide wireinto the side-branch vessel passage.

The bifurcated catheter assembly can be used at an arterial bifurcationboth for PTCA and for stent delivery and implanting. Other features andadvantages of the present invention will become apparent from thefollowing detailed description, taken in conjunction with theaccompanying drawings, which illustrate, by way of example, the featuresof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a diseased arterial bifurcation;

FIG. 2 is a sectional view of an arterial bifurcation showing a priorart single balloon catheter used to dilate the main vessel.

FIG. 3 is an sectional view of an arterial bifurcation showing two priorart balloon catheters used to simultaneously dilate both the main andside branch vessels.

FIG. 4 is an sectional view of an arterial bifurcation showing a priorart Y-shaped balloon used to dilate both the main and side branchvessels.

FIG. 5 is a side elevational view of a bifurcated dilation catheterembodying the present invention.

FIG. 6 is a cross-sectional view in enlarged scale taken along the line6—6 in FIG. 5 of the proximal portion of the main catheter body.

FIG. 7 is a cross-sectional view in enlarged scale taken along the line7—7 in FIG. 5 of the distal portion of the main catheter body.

FIG. 8 is a cross-sectional view in enlarged scale taken along the line8—8 in FIG. 5of the proximal portion of one of the catheter branches.

FIG. 9 is a cross-sectional view in enlarged scale taken along the line9—9 in FIG. 5 of the distal portion of one of the catheter branches.

FIG. 10 is a sectional view of an arterial bifurcation showing bothballoons dilated during PTCA.

FIG. 11 is a sectional view of an arterial bifurcation showing theinvention deploying a stent.

FIG. 12 is an elevational view of the bifurcated catheter assemblyshowing the catheter branches coupled together.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention includes an assembly and method for treatingbifurcations in the coronary arteries, veins, arteries and other vesselsin the body. As shown in FIG. 1, an arterial bifurcation is a sitewithin the vasculature of a body where an artery divides into two vesselpassages. FIG. 1 also illustrates how plaque can build up on the arterywalls creating a narrowing known as a stenosis. The stenosis can bedilated using a balloon catheter to compress the plaque against thevessel wall in a procedure known as PTCA. After the PTCA procedure, astent is deployed in the vessel to reduce the likelihood of thedevelopment of restenosis.

Prior art techniques for treating arterial bifurcations have proved lessthan satisfactory. For example, FIGS. 2-4 depict prior art techniquesfor treating arterial bifurcations which include using a single balloon,two single balloons and a Y-shaped balloon. Referring to FIG. 2, asingle balloon catheter is inserted into one branch of a bifurcation andis inflated to dilate the stenosis. Using a single balloon catheter totreat an arterial bifurcation requires dilating each vessel passage ofthe bifurcation individually. Using this approach, the dilation of thetreated passage may push against the wall of the untreated passagethereby impeding the blood flow to the untreated branch and also mayshift plaque from the treated passage to the untreated passage.Therefore, this technique is inadequate and often produces undesirableresults which can harm the patient.

Many physicians attempt to treat a bifurcation by employing a “kissingballoon” technique. Referring to FIG. 3, this prior art device andmethod uses two separate balloon catheters which are both inserted intoa guide catheter and track separate guide wires. One balloon is advancedinto each of the vessel passages at the bifurcation site and theballoons are simultaneously inflated to dilate a stenosis or to deliverand deploy two separate stents to the bifurcation site after the vesselshave been dilated. In practice, however, the use of two separate singleballoon catheters is cumbersome and it can be difficult for a physicianto manage both devices. In addition, the flow of contrast through theguide catheter is restricted by the presence of two catheter shaftswithin the guide catheter lumen thereby making it difficult for thephysician to view the area being treated.

As illustrated in FIG. 4, another prior art device includes a singlecatheter with a Y-shaped balloon at the distal end and has been proposedas an improved means for treating arterial bifurcations. The prior artdiscloses a Y-shaped balloon being advanced through the lumen of avessel and inflated at a bifurcation to dilate both passagessimultaneously or to implant a Y-shaped stent. Although the Y-shapedballoon would provide an improvement over the kissing balloonstechnique, the practicality of the proposed Y-shaped balloon is doubtfulbecause it presents manufacturing challenges, problems associated withpositioning (e.g. wire wrapping) and deployment at the bifurcation, andhigher profiles.

All of the prior art methods for treating an arterial bifurcationdepicted in FIGS. 2-4 have various drawbacks which have been solved bythe present invention.

Referring to FIGS. 5-10 and 12, the bifurcated catheter assembly of thepresent invention provides two separate balloons in parallel which canbe advanced into separate passages of an arterial bifurcation andinflated simultaneously to dilate stenoses or to deploy a stent. Thebifurcated catheter assembly 10 includes, generally, main catheter body11 with a proximal portion 12 having first inflation lumen 14 and firstguide wire lumen 16 extending therethrough. The proximal portion of themain catheter body preferably is a stainless steel tube surrounded by apolymer jacket (not shown) which can be formed of various materials toincrease lubricity including polyethylene, nylon, polyethyl etherketone, and copolyester-elastomer. An inflation hub 21 is located at theproximal end of the proximal portion of the main catheter body forattaching an inflation device.

In the preferred embodiment, the bifurcated catheter assembly is of therapid exchange type, which is known in the art. Referring to FIGS. 5 and6, first guide wire lumen 16 includes first exit port 18 which is at theproximal end of catheter assembly 10. Integrated guide wire 15 slidablyextends from outside first exit port 18 and into and through first guidewire lumen 16. As depicted in FIG. 7, second guide wire lumen 17 is ofthe rapid exchange type and is configured to slidably receive trackingguide wire 19. The second guide wire lumen exits catheter body 11 atsecond exit port 20.

Optionally, slit 13 could be provided in catheter body 22 between guidewire exit port 20 and a location just proximal of balloon 42. This wouldallow the catheter body to be “peeled away” from the tracking guide wire19 to allow for more convenient catheter exchange.

The proximal portion 12 of main catheter body 11 is connected to distalportion 22 of main catheter body 11. The distal portion of the maincatheter body preferably is formed from a polymer material to provideincreased flexibility in the distal portion of the catheter. The distalportion of the main catheter body includes an extension of firstinflation lumen 14 for carrying inflation media, first guide wire lumen16 containing integrated guide wire 15 and second guide wire lumen 17containing tracking guide wire 19. The connection 30 between theproximal portion and the distal portion of the main catheter body allowsfor the continuous flow of inflation media between the proximal anddistal portions with no leaks.

A cross-section through catheter branch 32 appears as FIG. 8. Catheterbranch 34 has a similar cross-sectional configuration.

The distal portion 22 of main catheter body 11 is connected to first andsecond parallel catheter branches 32 and 34, respectively. Theconnection 36 between the distal portion of the main catheter body andeach of the parallel catheter branches allows for continuous flow ofinflation media from the first inflation lumen in the distal shaft tosecond and third inflation lumens 37,38 in each of the catheterbranches. The parallel catheter branches 32,34 respectively containsecond and third inflation lumens 37,38 for communicating inflationmedia and first and second guide wire lumens 16,17 for carrying theintegrated 15 and tracking guide wires 19. The first and second catheterbranches have distal tips 46,48, respectively, through which the guidewires exit the guide wire lumens. The tracking guide wire 19 exits fromdistal tip 46 of first catheter branch 32 and integrated guide wire ISexits from distal tip 48 of second catheter branch 34. As shown in FIG.12, attached to the side of the distal end of second catheter branch 34is a coupling device 54 in the form of a short tube. During advancementof the catheter assembly, the tracking guide wire 19 exits the firstcatheter branch 32 and is threaded through the coupling device in thesecond catheter branch 34 to hold the two catheter branches together.

Mounted on catheter branches 32,34, are respective expandable memberspreferably in the form of balloons 42,44. The balloons can be formed ofmany different materials including polyethylene, polyolefin copolymer,polyethylene teraphthalate, nylon, and PeBax. Inflation hub 21 receivespressurized inflation fluid and supplies the inflation fluid toinflation lumens 14, 37 and 38. Each catheter branch includes inflationnotch 50,52, respectively, which allows inflation media to exit thecatheter and inflate the expandable members.

In the preferred embodiment, the overall catheter is about 135 cm to 150cm long, and the main catheter body between inflation hub 21 andconnection 30 is about 125 cm in length. The proximal portion of themain catheter body preferably has a diameter of about 0.75 mm and thedistal portion of the main catheter body between connection 30 and 36has a diameter of about 1.5 mm. The first catheter branch 32 preferablyis about 10 cm in length with a diameter of about 1 mm and the secondcatheter branch 34 is about 12 cm in length with a diameter of about 1mm. Typically, the expandable members are balloons which are preferablyfrom about 1.5 mm to about 4.5 mm in diameter when expanded and areabout 20 mm in length, for treating coronary arteries. The foregoingdimensions will vary greatly depending upon the particular applicationand body lumen being treated.

The assembly of the present invention is configured for low profiledelivery without compromising pushability and trackability over bothguide wires. The proximal portion 12 of main catheter shaft 11 may bemade by necking the jacket material over the stainless steel tubing. Thejacketed tube is then connected to the distal portion 22 of the maincatheter shaft. Mandrels are inserted into the guide wire lumens 16, 17and inflation lumens to prevent the lumens from collapsing during thefusing phase when heat is applied and the proximal portion is heat fusedto the distal portion of the main catheter shaft. After junction 30 hascooled, the mandrels are removed leaving continuous and leak-proofinflation lumens which extend all the way through the catheter assemblyshaft.

Each of parallel catheter branches 32 and 34 is constructed as isstandard in the art of catheter assembly. Balloons 42 and 44 areattached to each of the branches using a known technique such as heatseal, adhesive, laser weld, or solvent bond or the balloons are formedas one piece out the same tubing material as catheter branches. The twoparallel catheter branches are then connected to the distal portion ofthe main catheter body similarly using heat to complete the assembly.The method of assembly of the catheter may vary depending upon availablematerials and manufacturer preferences.

In operation, tracking guide wire 19 is inserted percutaneously into,for instance, the femoral artery and is maneuvered to the bifurcationsite such that the distal end of the tracking guide wire is in the mainvessel passage distal to the bifurcation. The proximal end of trackingwire 19 is inserted into the short tube of coupling device 54. Theproximal end of tracking wire 19 is then inserted into distal tip 46 ofcatheter branch 32. Passing tracking wire 19 through the tips of bothbranches together. This allows for smooth, uninterrupted movement of thecatheter to the target site. The bifurcated catheter assembly 10 is thenadvanced over the tracking guide wire such that balloons 42 and 44 arein the main vessel passage just distal to the bifurcation. Because thisinvention is a rapid-exchange type of catheter, a portion of thetracking guide wire 19 is located external to the catheter and thereforethere is very little frictional drag during advancement of the assembly.When the balloons have been advanced distally beyond the bifurcation,the tracking guide wire 19 is withdrawn proximally until its distal endpulls out of coupling device 54 thereby decoupling the balloons fromeach other. Tracking wire 19 is then advanced back through tip 46 intothe main vessel passage. The bifurcated catheter assembly is thenwithdrawn proximally along the tracking guide wire so that the balloonsare proximal to the bifurcation. With the tracking guide wire still inthe main vessel passage, the integrated guide wire, which has beencontained within second guide wire lumen 17, is advanced from the distaltip of the other catheter branch 34 into the side-branch vessel. At thispoint, there is one guide wire exiting the distal tip of each catheterbranch and entering a separate passage of the bifurcation whereby thetracking guide wire is in the main vessel passage and the integratedguide wire is in the side branch vessel passage. The catheter assemblyis then advanced over the guide wires whereby each balloon tracks aguide wire into a separate passage of the bifurcation until the balloonsare positioned at the stenosed areas.

An inflation syringe (or pump) located outside the patient's body isattached to inflation hub 21 and supplies pressurized inflation mediathrough the inflation lumens and into balloons 42 and 44. With oneballoon in each passage, the balloons can be simultaneously inflated todilate a stenosis during a PTCA procedure as illustrated in FIG. 10.Because both passages of the bifurcation are treated simultaneously,neither of the passages is pinched off or damaged by the procedure. Inaddition, all the plaque in the bifurcation is compressed at the sametime and therefore there is no shifting of plaque from one passage tothe other. After the stenosed areas have been dilated, the balloons aredeflated to their minimum dimensions so that they can be easilywithdrawn from the vessels.

In the preferred embodiment shown in the figures, the device could beremoved together with integrated wire 17, while tracking wire 19 remainsin the main vessel passage. This is facilitated by the rapid exchangeconfiguration of the device, wherein tracking wire 19 exits catheterbody 22 through exit port 20, which is located about 25 cm proximal fromthe distal end of the balloon.

The slitted configuration mentioned above would further facilitate arapid exchange procedure. Optionally, lumen 16 through which integratedwire 17 passes, could be provided with a rapid exchange guide wire exitport on the catheter body. This would allow the maintenance of each wirein position in their respective vessels during catheter exchange. As afurther option, lumen 16 could also be slitted to further facilitaterapid exchange. In this case a second guide wire exit port would beprovided distal of the proximal hub.

Another advantage of the invention is the ability to deliver and implanta Y-shaped stent to the bifurcation as shown in FIG. 11. In thisprocedure, the bifurcated catheter assembly 10 has Y-shaped stent 60mounted on the balloons. The balloons 42 and 44 are held together duringdelivery to provide a low profile allowing room for radiopaque dye to beinjected into the bloodstream during the procedure. The tracking guidewire is advanced into the main vessel to a point distal of thebifurcation. The bifurcated catheter assembly is then advanced over thetracking guide wire so that the stent is distal to the bifurcation. Thetracking guide wire is then withdrawn proximally thereby decoupling theballoons. The catheter assembly is then withdrawn proximally until it isproximal to the bifurcation with the tracking guide wire remaining inthe main vessel. The integrated guide wire is then advanced out ofbranch catheter 34 and into the side-branch vessel. The catheterassembly is advanced over both guide wires until the balloons and stentare anchored in the bifurcation. The balloons are inflated and the stentexpanded and implanted in the bifurcation.

From the foregoing, it will be appreciated that the bifurcated catheterassembly of the invention allows both passages of a diseased bifurcationto be dilated simultaneously during a PTCA procedure, thereby avoidingany possible damage to the vessels and avoiding the transfer of plaquefrom one passage to the other. The bifurcated catheter assembly alsofacilitates the delivery and deployment of a Y-shaped stent which isdesigned specifically for use in a bifurcation. The invention is made ofmaterials commonly used in the industry today and is simple to use andeasy to manufacture.

While a particular form of the invention has been illustrated anddescribed, it will be apparent that various modifications can be madewithout departing from the spirit and scope of the invention.

What is claimed is:
 1. A method for delivering a bifurcated catheterassembly in a patient for treating a bifurcated vessel having a mainvessel and a side-branch vessel, the method comprising: a. providing abifurcated catheter assembly having i. an elongated main catheter bodyhaving a proximal end and a distal end; ii. a first catheter branchhaving a proximal end and a distal end, the proximal end being connectedto the distal end of the main catheter body, the first catheter branchhaving a first expandable member and having a rapid exchange guide wirelumen extending through the first catheter branch; iii. a secondcatheter branch having a proximal end and a distal end, the proximal endbeing connected to the distal end of the main catheter body, the secondcatheter branch having a second expandable member and having anover-the-wire guide wire lumen extending through the second catheterbranch and the main catheter body; iv. a first expandable memberassociated with the first catheter branch; v. a second expandable memberassociated with the second catheter branch, wherein a stent is mountedon the first and second expandable members; vi. a coupler mounted on thefirst catheter branch for releasably coupling the first catheter branchto the second catheter branch; b. providing a first rapid exchange (Rx)guide wire and a second over-the-wire (OTW) guide wire; c. inserting thefirst Rx guide wire into the Rx guide wire lumen of the first catheterbranch and inserting the distal end of the first Rx guide wire into thecoupler; d. inserting the second OTW guide wire into the OTW guide wirelumen of the second catheter branch; e. advancing the catheter over thefirst Rx guide wire and simultaneously carrying the second OTW guidewire in the OTW lumen of the second catheter branch; f. advancing thefirst Rx guide wire into the main vessel and advancing the catheter overthe first Rx guide wire thereby positioning the catheter distal enddistal of the bifurcation; g. withdrawing the first Rx guide wireproximally so that the distal end of the first Rx guide wire withdrawsfrom the coupler thereby uncoupling the first expandable member from thesecond expandable member; h. advancing the distal end of the second OTWguide wire distally of the catheter distal end and into the side branchvessel; i. withdrawing the catheter proximally so that the catheterdistal end is proximal of the vessel bifurcation; j. advancing thecatheter over the first Rx and the second OTW guide wires so that atleast a portion of the stent is positioned in the first and the secondvessels; k. inflating the first and the second expandable members andsimultaneously expanding and implanting the stent in the vessels formingthe bifurcation; l. deflating the first and the second expandablemembers; m. withdrawing the catheter from the patient.
 2. The method ofclaim 1, wherein the first and the second expandable members aresimultaneously inflated.
 3. The method of claim 1, wherein the firstbranch catheter has a slit so that the first Rx guide wire can be pulledthrough the slit when the catheter is withdrawn from the patient.